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Session 49 - The Frontiers of Far Ultraviolet Astrophysics - I.
Topical, Oral session, Wednesday, June 10
Sierra/Padre,
Molecular hydrogen (H_2) is the most abundant constituent in the interstellar medium, but cannot be observed directly except through its electronic transitions in the far-UV. To date UV observations of interstellar H_2 exist only for stars observed with the Copernicus satellite, which was limited to visual extinctions of 1 magnitude or less, and a few additional sources observed (often at lower resolution) with other instruments. Important gains can be made through the measurement of interstellar H_2 absorption of more heavily-reddened lines of sight, which can provide information on the total gas column densities (which are needed for analyses of abundances and depletions), chemical models, the effects of differing grain properties; and measurements of cloud physical conditions such as kinetic temperature, density, and radiation field intensity. The FUSE mission will provide data on interstellar H_2 for stars with total extinctions up to 5 magnitudes, lying behind material with a variety of extinction, chemical, and physical conditions, thus providing new information on the chemistry and physics of translucent interstellar clouds. This talk will provide a brief review of previous work on UV spectra of interstellar H_2, and will then focus on future work that is possible with FUSE and other potential far-UV observatories.
